JERUSALEM — A "terror group" abducted three teens, including a U.S. citizen, who disappeared in the West Bank, Israel's prime minister said Saturday, as soldiers searched the territory to find them.

Prime Minister Benjamin Netanyahu again blamed the Palestinian Authority for the Thursday night disappearance of the teens. Palestinian officials said they are assisting Israeli forces, who assessed surveillance footage Saturday, and arrested more than a dozen Palestinians.

Netanyahu made a televised address Saturday night, local time, after meeting with top security officials, saying Israeli forces were conducting "intensive operations" to locate the teens, and bring them home. "Our children were kidnapped by a terror group," he said. "There is no doubt about that."

Netanyahu said he directed Israel's security branches to use all means at their disposal to find the abducted teenagers, and "prevent the possibility of their transfer to the Gaza Strip or anywhere else."

The Israeli military identified the teens as Naftali Frenkel, 16, Gilad Shaar, 16, and Eyal Yifrach, 19. Israeli television station Channel 10 named Frenkel as the U.S. citizen that officials mentioned earlier. They were reportedly hitchhiking home when they were abducted.

Their kidnapping would be the biggest abduction of its kind by Palestinian militant groups in recent memory in the West Bank. Israeli-Palestinian tensions already were strained in part because of the recent formation of a Palestinian unity government that has the backing of the Islamic militant group Hamas.

Israeli Defense Minister Moshe Yaalon said Saturday that Israel has thwarted more than a dozen kidnapping attempts by Palestinian militants so far this year.

"It appears this event slipped under our radar, but we will not rest until we free the youths and put our hands on the terrorists who are responsible for this operation," Yaalon said. "As long as we don't know otherwise, our working assumption is that they are alive."

Hamas, branded a terror group by the West for its attacks aimed at civilians, has been involved in kidnappings of Israelis in the past. The group routinely claims responsibility if involved in an attack, but has not yet claimed taking the teens.

Netanyahu said Palestinian President Mahmoud Abbas must do everything necessary to help return the teens. He said Abbas is responsible for any attack on Israel, whether it emanates from the West Bank or Gaza.

"It's impossible to talk peace with Israel while simultaneously form a unity government with Hamas, a terror group committed to destroying Israel," Netanyahu said.

However, Palestinian officials have rejected Netanyahu's contention that the Palestinian Authority, a self-rule government that administers 38% of the West Bank, was responsible for the fate of the teens. They noted that the three went missing in an area of the West Bank that is under full Israeli control.

Despite the charged rhetoric, Palestinian security forces were cooperating with their Israeli counterparts to try to find the teens, a Palestinian official said.

Abbas has said security coordination in the West Bank between Israel and the Palestinians, usually aimed at tracking down Islamic militants, will continue despite the unity government.

Meanwhile, three different claims of responsibility emerged in the West Bank, though it's not clear if any were authentic.

In one leaflet, a group portraying itself as a branch of an al-Qaeda splinter group said it kidnapped the three to avenge the killing of three members in a clash with Israeli security forces in the Hebron area earlier this year. Another statement purportedly came from the Al Quds Brigades, the military wing of the Palestinian group Islamic Jihad.

Israel's military has warned soldiers and civilians not to accept rides from strangers, but hitchhiking remains common.

An Israeli intelligence official said more than 50 kidnapping attempts were thwarted at various stages of execution in 2013 alone. The official spoke anonymously, as he is not allowed to brief the media.

Two of the three missing teens are from settlements in the West Bank, territory Israel captured from Jordan in the 1967 Mideast war, and that Palestinians are demanding as part of their future state along with the Gaza Strip and east Jerusalem.

Hamas ruled Gaza for seven years, after violently taking over the territory from the Palestinian Fatah group in 2007, and remains the de facto power there despite the unity deal.

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